Electrical circuits of various kinds are susceptible to a number of unfavorable conditions. For example, in an on/off switch, arcing or sparking may occur between electrical contacts when such paired contacts bounce or partially separate upon toggling the switch to the off position. This condition is referred to as a teasable condition in an electrical system. Furthermore, the contacts of such an electrical system may weld together causing the circuit to remain closed even after the switch has been in the off position for a number of cycles.
Such an on/off switch is commonly used in the triggers of hand operated devices such as main line powered construction tools and latterly powered gardening tools. In these types of devices, the contact pressure directly relates to the trigger travel (i.e., the distance over which the trigger is moved or depressed). The user directly controls the trigger travel by pulling and relaxing his finger over the trigger. However, the contact pressure between electrical contacts in the switch may approach zero when a user only partially toggles the trigger to the on position. In extreme cases, if a tool operator holds the trigger in the on position while current is running through the contacts at near zero contact pressure, the contacts may weld together. In such circumstances, even after the operator has released the trigger, the circuit will remain closed. The powered tool cannot be turned off easily, causing a safety hazard. This condition poses potential hazards to nearby materials, equipment and to humans, including the operator.
There is a need for an invention that can quickly provide full contact pressure between the electrical contacts and that can cause the electrical contacts to disconnect quickly. Thus, there is a need for an invention in which the contact pressure does not depend upon the trigger travel so as to avoid teasing after the switch is turned on.